Systems for recovering waste water for repeated use conventionally include the following stages through which the water being treated passes at least once. A tank for holding the waste water is connected through a pump to mechanical filters which in turn communicate with a reverse osmosis stage. The output of the reverse osmosis stage leads to an active charcoal treatment stage. The output of the charcoal stage is connected to a disinfection stage.
In connection with passenger aircraft and to some extent also in connection with cargo aircraft, there exists the continuous need for improving the comfort of the passengers and/or crew. This need conflicts with the limited loading capacity of an aircraft, because, on the one hand, as much water as possible should be taken along for drinking and other purposes, while on the other hand, the water volume to be carried along should be minimized to increase the payload. As a result, it is necessary to optimally utilize the water quantity that can be taken along under economically feasible conditions, for example, for satisfying ever increasing comfort requirements such as the provision of washing and even showering facilities on long distance flights. On short distance flights the need for reducing the water quantity to an absolute minimum is even larger. Thus, there is room for improvement in the just outlined area as well as other areas where large quantities of drinking quality water are not readily available.
An article entitled "Integrated Water and Waste Management System for Future Spacecraft" by A. L. Ingelfinger et al., was published in "Transactions of the ASME", Journal of Engineering for Industry, Vol. 97, No. 1, February 1975, pages 224 to 227, in which a solution of the above outlined problem is suggested for spacecraft. More specifically, waste water treatment is accomplished by a method in which substantially evaporation is employed in combination with a catalytic oxidation of components suspended in the water. This approach requires substantial heat that is produced by using radioactive isotopes. Thus, the known method has the disadvantage that the radiation required for the waste water treatment is not suitable for passenger aircraft due to safety and health reasons. Furthermore, the required high energy consumption of the known apparatus for the waste water treatment is available only by using atomic energy, but becomes unfeasible if other sources of energy must be used for the above evaporation and catalytic oxidation.
Another solution to the above outlined problems is disclosed in German Patent Publication (DE-PS) 3,715,759, published on Dec. 21, 1989, relating to a water supply system, especially for use on board of an aircraft. The known system passes the waste water through a plurality of stages until drinking water quality is achieved. The known system includes a mechanical filter, a pump, a charcoal filter including activated charcoal, an ozone stage, and a reverse osmosis stage followed by a disinfecting stage. The just mentioned known system has the disadvantage that for a sufficiently high cleaning effect in the ozone stage, substantial contact times are required for treating the waste water with ozone. Another disadvantage is seen in that the substantial space is required if the known system is of a size that assures a commercially feasible throughput volume through the known system.
So-called freeze concentration reactors are known for use in chemical and food processing. However, heretofore such reactors have not been used for waste water treatment in aircraft nor in spacecraft.